Video monitoring and display systems are used in a wide range of applications including in driver assistance systems for motor vehicles. Some vehicles are equipped with video cameras at various locations in the vehicle to assist a vehicle operator in viewing regions around the vehicle that are otherwise difficult to see. For example, a backup camera mounted at the rear of the vehicle generates a video of the region behind the vehicle and an in-vehicle video display presents the view to the vehicle operator. The video from the in-vehicle camera often shows so-called “blind spots,” which are portions of the area behind the vehicle that are not readily seen through conventional windows or mirrors. The camera systems provide additional visibility to the vehicle operator to reduce or eliminate blind spots while the vehicle is in operation.
Some in-vehicle video systems send video data from a camera to a video display device through a wired communication medium in the vehicle. Other video systems transmit video data from a camera using a wireless transceiver that sends the video data to another wireless transceiver that is connected to the video display device. Some wireless video monitoring systems are used as after-market video monitoring systems for vehicles that did not receive a video monitoring system at the time of manufacture. Other wireless video monitoring systems are included in new vehicles to reduce the complexity of running data wires in the vehicle and to enable transmission of video data to portable electronic devices such as smartphones, tablet computers, and other portable electronic devices that are available to the vehicle operator.
Wireless communication systems for transmission of video data in a motor vehicle can provide additional information to a vehicle operator during operation of the motor vehicle, but the environment and operating requirements for a motor vehicle present challenges to the design of wireless video transmission systems. While numerous systems for transmission of video data over wired and wireless networks, including streaming data using H.264 compression or other temporal compression schemes are known to the art, the existing video streaming systems are not always suitable for use in motor vehicle systems that require rapid real time presentation of images that are generated by backup cameras or other cameras in the vehicle. For example, video streaming and compression systems typically generate segments of video in a short duration, such as a few seconds, and then encode each video segment using inter-frame compression techniques. That is to say, the compression process analyzes data from multiple frames of recorded video data that occur over a predetermined period of time and generates compressed data where the decompression process for some frames of video require the prior decompression of previous frames in the video sequence. Video compression and streaming techniques that are known to the art, even so-called “live” video streams such as two-way video communication and camera monitoring systems, commonly compress segments of several video frames and use buffering techniques to provide smooth video playback. Buffering occurs when a receiving device receives multiple frames of video prior to displaying the video frames to ensure that the playback of video remains smooth even if a transient interruption in network service delays transmission for portions of the video.
While buffering is an effective technique for many video streaming systems, existing buffering techniques can be less effective for use with backup cameras or other cameras that show present-time conditions around the vehicle with minimal time delay for display of the images from the in-vehicle cameras. Additionally, motor vehicles often operate in electrically noisy environments with transient electrical noise sources that affect the video data stream in unpredictable ways during operation.
During operation of the motor vehicle, the wireless video transmission system should operate with high reliability to ensure that the vehicle operator can view an accurate depiction of the video from the in-vehicle camera, even in the presence of interference. Consequently, improvements to wireless transmission systems and methods to enable reliable transmission of video data for a wide range of operating conditions in and around the vehicle would be beneficial.